I started with a Crosman sliding barrel bb gun. Then a Benjamin pump, then a Crosman pumper. I still remember when Boy's Life had a maturity checklist you could show your parents that showed you were ready for a Daisy.
In MI, you need to be 12, and have had Hunter Ed to hunt small game, so, the boys are bigger when firearms enter the picture.
I think starting a kid on a .410 teaches them to aim their shotgun. Not swing it.
I started all of my girls on a 20 ga Mossberg 500 Youth model with a sorbothane pad. The Mossy pump allowed single loading, and has cast which made it fit far better than the Remmies or Brownings. The 20ga youth autos are very heavy, and persnickety about loads. The H&R type 28's and 20's used at our gun club swing poorly, and are so light they pound the smaller kids.
And of course, a majority of women are cross dominant.
Starting kids in a duck blind is an excellent way to manage the transition from classroom to field in all matters safety.
I've been there when kids have had accidental discharges. I never like it, and avoid hunting with Dad's that want to bring armed 10 year olds. I often think it's Dad's wishful thinking that put's custom 243's or doubles in the hands of such young children.